Various inkjet printing arrangements are known in the art and include both thermally actuated printheads and mechanically actuated printheads. Thermal actuated printheads tend to use resistive elements or the like to achieve ink expulsion, while mechanically actuated printheads tend to use piezoelectric transducers or the like.
A representative thermal inkjet printhead has a plurality of thin film resistors provided on a semiconductor substrate. A nozzle plate and barrier layer are provided on the substrate and define the firing chambers about each of the resistors. Propagation of a current or a “fire signal” through a resistor causes ink in the corresponding firing chamber to be heated and expelled through the appropriate nozzle.
Ink is typically delivered to the firing chamber through a feed slot that is machined in the semiconductor substrate. The substrate usually has a rectangular shape, with the slot disposed longitudinally therein. Resistors are typically arranged in rows located on both sides of the slot and are preferably spaced an approximately equal distances from the slot so that the ink channel length at each resistor is approximately equal. The width of the print swath achieved by one pass of a printhead is approximately equal to the length of the resistor rows, which in turn is approximately equal to the length of the slot.
Feed slots are typically formed by sand drilling (also known as “sand slotting”). This method is preferred because it is a rapid, relatively simple and scalable (many substrates may be processed simultaneously) process. While sand slotting affords these apparent benefits, sand slotting is also disadvantageous in that it causes micro cracks in the semiconductor substrate that significantly reduce the substrates fracture strength, resulting in significant yield loss due to cracked die. Low fracture strength also limits substrate length which in turn adversely impacts print swath height and overall print speed.
As new printer systems are developed, a key performance parameter is print speed. One way of achieving higher print speed is to increase the width of the print swath of a printhead. One potential manner of increasing print swath width is to increase the length of the substrate and the feed slot therein. Due to micro cracks and other structural defects induced during sand slotting, however, substrates are rendered too fragile to be further extended.
A need thus exists for a machined semiconductor substrate that has increased fracture strength to better withstand the thermal and mechanical stresses induced in ink jet printhead manufacture and use. A need also exists for a printhead semiconductor substrate that has increased fracture strength and can therefore be elongated to achieve longer print swath width. A need further exists for a machined semiconductor substrate for any intended purpose that has increased fracture strength.